The invention relates to a valve closing device having a driven shaft and having an input shaft which is coupled to the driven shaft and by means of which the driven shaft is drivable in normal operation, and having an emergency drive, wherein the driven shaft is transferrable additionally by the emergency drive from a position of use into an end position.
The invention further relates to a valve actuating assembly having an actuating drive for actuating, in the event of mains operation, a driven shaft which is operatively connectable or operatively connected to a valve and having a valve closing device for actuating the driven shaft in the event of mains failure.
These types of valve closing devices are known, for example, from technical systems in which a mass flow is controlled or regulated by means of valves. In this connection, the valves are actuated in normal operation by way of corresponding actuating drives. In the event of a mains failure, for example in the event of an electric power failure or in the event of a failure of a hydraulic or pneumatic supply to the actuating drives, the valve closing devices serve for the purpose of transferring the driven shaft into a pre-defined end position in order to transfer the valve connected in each case into a defined end state, for example into an open state or a closed state.
In order to be independent of the power supply via the already mentioned mains system, it is known in the event of mains failure to store the energy that is necessary for transferring the driven shaft into the desired end position in a mechanical manner using a spiral spring or a coil spring.
The known valve closing devices are used as an assembly part or are integrated into valve actuating assemblies of the type described in the introduction.
A defined torque is necessary, as a rule, to actuate the valve. In the case of the known emergency drives with mechanical energy storage in a spiral or coiled spring, the torque that can be developed by the emergency drive to actuate the driven shaft reduces during the energy releasing operation. The spiral or coiled spring consequently has to be sized such that there is still enough torque developed even at the end of the actuation movement. Conversely, this means that a tensioning device for tensioning the emergency drive has to be sized large enough such that even the spring force close to the tensioned state of the emergency drive is overcome. This tensioning device consequently has to be sized large enough, as a rule, such that a multiple of the torque that is actually necessary for actuating the driven shaft is able to be developed. The emergency drive is frequently tensioned by the already mentioned actuating drive for normal operation, the result of which is that the actuating drive is oversized for its usual tasks.